A cylindrical copper conductor with radius $r_1$ carries a current $I$. If the radius is doubled to $2r_1$ while keeping the current the same, and assuming the electric field within the conductor remains uniform, how does the drift velocity of electrons change?

If the electric current through an electric bulb is ${\rm{3}}{\rm{.2 }}\,{\rm{A}}$, the number of electrons flow through it in one second is

In a closed circuit, the current $I$ (in ampere) at an instant of time t(in second) is given by $I = 4 - 0.08\,\,t$. The number of electrons flowing in ${\rm{50}}\,\,{\rm{s}}$ through the cross-section of the conductor is